The main problem with AC motors is that they run in a constant series of shove-coast cycles. They don't run at a steady speed, they're shoved around and then coast, like those hand-powered merry-go-rounds we rode on as young kids in the playground. This is called the "cogging effect" and all AC motors have it, no exceptions. The effects can be minimized by choosing a motor with more poles. More poles per revolution = smaller shoves and shorter coasts between shoves. Another approach utilizes very low torque motors, thus reducing the effect of each shove. A third approach uses very high RPM motors, often in conjunction with a flywheel. Rubber or neoprene belts are usually specified, the idea being that the stretch in the belt will shield the platter from from unavoidable speed irregularities from the AC motor. AC motors are also sensitive to input frequency, so a speed controller circuit that stabilizes power frequency is helpful.
DC motors accelerate at a steady rate. No cogging effects. Their downsides include sensitivity to input voltage and a tendency to drift away from a preset speed. Input voltage can be controlled with a good power conditioner. Speed drift is only controlled, as far as I know, by the unique motor controller of the Teres tables, which reads a strobe on the platter and adjusts input voltage to the motor accordingly.
Hope that's helpful in a general way, but if choosing a table is what you're trying to do, specifying a budget and musical tastes and goals would get some more real-world responses. You certainly shouldn't choose a TT simply on the basis of motor type. There are other factors of equal or greater importance.
DC motors accelerate at a steady rate. No cogging effects. Their downsides include sensitivity to input voltage and a tendency to drift away from a preset speed. Input voltage can be controlled with a good power conditioner. Speed drift is only controlled, as far as I know, by the unique motor controller of the Teres tables, which reads a strobe on the platter and adjusts input voltage to the motor accordingly.
Hope that's helpful in a general way, but if choosing a table is what you're trying to do, specifying a budget and musical tastes and goals would get some more real-world responses. You certainly shouldn't choose a TT simply on the basis of motor type. There are other factors of equal or greater importance.